What is guano and how can I tell it apart from mouse droppings?

Guano is another term for bat excrement. It is similar in shape and size of mouse droppings and can be easily confused. Guano is easy to determine with a flashlight or other lighting means. If you crush it with a gloved hand and shine a light on the material left and it sparkles it is most likely guano. This is due to the exoskeletons of the insects that bats feed on nightly. Guano also has a smell often described as pungent, acrid or musty. It is often referred to as a smell that one will not forget.